Backpack



FIG. 1 is a top front perspective view of a backpack showing the claimed design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The dot-dash broken lines in the figures show portions of the backpack that form no part of the claimed design.

The dashed broken lines in the figures show stitching and form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 